When we first read this verse, most of us think that Jesus is talking about miracles, signs, wonders, and healings, that is, that those of us who really believe in Him will be able to do those great works. However, He may not be thinking only about such grand acts.
He is probably also suggesting that the great works we will do are the day-to-day works of Christian living—not necessarily the ones that will make the lead story on the evening news. He means things like having good relations with one's spouse and children. He means overcoming a sin and growing in character. He means helping others in their walk toward the Kingdom of God. In the end, these are far greater works than miracles and spectacular healings.
Consider the twelve apostles. How many people did Jesus convert during His ministry? Acts 1:15 tells us that the number of disciples was only 120. Yet, just a few pages later, we find that the apostles did even greater works, baptizing 3,000 on Pentecost (Acts 2:41) and 5,000 on another day (Acts 4:4). People were saying that the apostles had "turned the world upside down" (Acts 17:6)! Their greater works were preaching the gospel, feeding the flock, and helping others to overcome and grow toward the Kingdom of God. Sure, they did their share of miracles, but their most lasting, eternal works were their preaching and their Christian sacrifices for the gospel.
Jesus said no one was greater than John the Baptist (Matthew 11:11), and what did he do? He did not perform one miracle, but he preached repentance (Matthew 3:1-2), which is a great work. It makes people realize that they are sinful and that they need a Savior to redeem them and to help them turn their lives around. Many were baptized and later followed Christ.
We need to apply this personally. What great works are we supposed to do? They may be mundane—overcoming sin, growing in character, producing spiritual fruit, and encouraging others in their walk with God—but they are the day-to-day Christian activities that, in the end, will assure that not only will we be in the Kingdom but those we love and fellowship with will be too. Those are truly great works! "Miraculous" works may be flashy and draw a lot of attention, but the greatest works are the ones with eternal consequences, those that help others maintain a firm grasp on salvation.
In Acts 10:38, Peter pares the life of Christ down to just a few insightful phrases: ". . . how God anointed Jesus of Nazareth with the Holy Spirit and with power, who went about doing good . . ." That is the gist of His life: He did good with every minute He lived. The apostle Paul gives us similar marching orders in Galatians 6:10: "Therefore, as we have opportunity, let us do good to all, especially to those who are of the household of faith." If we follow this advice, following in the footsteps of Jesus Christ, we will one day be where He is.